Multifunctional polymerization initiators from allyl-substituted tertiary amines

ABSTRACT

A MULTIFUNCTIONAL POLYMERIZATION INTIATOR IS FORMED ON ADMIXING AN ALLYL-SUBSTITUTED TERTIARY AMINE AND ORGANOMONOLITHIUM COMPOUND, OPTIONALLY WITH THE FURTHER ADDITION OF A SOLUBILIZING MONOMER.

United States Patent @fice 3,652,456 MULTIFUNCTIONAL POLYMERIZATION INITIA- TORS FROM ALLYL-SUBSTITUTED TERTIARY AMINES Floyd E. Naylor, Bartlesville, Okla., assignor to Phillips Petroleum Company No Drawing. Filed June 9, 1969, Ser. No. 831,753 Int. Cl. C07f 1/02 US. Cl. 252-431 5 Claims ABSTRACT OF THE DISCLOSURE A multifunctional polymerization initiator is formed on admixing an allyl-substituted tertiary amine and organomonolithium compound, optionally with the further addition of a solubilizing monomer.

This invention relates to a new multifunctional polymerization initiator which forms as the reaction product from reacting allyl-substituted tertiary amines and organomonolithium compounds. In another aspect, it relates to a polymerization process whereby gel-free, low vinyl-containing polymers, with a reduced tendency to coldfiow can be produced.

Dilithium and monolithium polymerization initiators are well known to the art. Likewise, many of these are known as compounds that present particular difiiculties in preparation and storage. These known initiators often require a polar diluent for their preparation and are sufficiently unstable that they cannot be prepared and subsequently stored for very long without a loss in initiator activity. Attendant to these difiiculties is the fact that the polymers prepared with these heretofore known lithium-based initiators often exhibit undesired coldflow tendencies; and block copolymers similarly prepared often exhibit low green tensile strengths.

It has now been discovered that by reacting an organomonolithium compound with an allyl-substituted tertiary amine that a surprising and versatile multifunctional polymerization initiator is produced. The conjugated diene polymers prepared with the multifunctional initiators of this invention exhibit little, if any, coldfiow and are relatively free of gel. It is equally surprising that these polymers, when prepared in a hydrocarbon medium according to this present invention, possesss relatively low vinyl content. Block copolymers prepared from conjugated dienes and monovinyl-substituted aromatic hydrocarbons produced according to this invention have demonstrated relatively high green tensile strength in contrast to those prepared with the monolithium initiator such as n-butyllithium.

It is an object of this invention to provide a new lithiumbased initiator. It is an object of this invention to provide a stable initiator so as to enable easy storage thereof. It is an object of this invention to provide an improved process for the polymerization of polymerizable conjugated dienes. It is an object of this invention to provide a method whereby conjugated dienes can be polymerized in the presence of a multifunctional organolithium initiator so that the polymeric product produced thereby has a reduced tendency to coldflow. Another object of this invention is to provide an improved block copolymer possessing high Mooney viscosity values and exhibiting high green tensile strength. Other objects of this invention are to produce a polymeric product which is gel-free, has a low vinyl content and possesses a reduced tendency to coldfiow. Other objects, advantages, and features of my invention will be apparent to those skilled in the art from the following discussion and examples herein set forth.

Patented Mar. 28, 1972 According to my invention multifunctional polymerization initiators are prepared by reacting an organomonolithium compound with an allyl-substituted tertiary amine. The initiators of this invention are multifunctional in that they are branched and the branches are terminated with lithium substituents which serve as reactive sites for polymerization initiation. These multifunctional initiators contain at least two carbon-lithium bonds and when polymerizations are initiated in the presence of these compounds branched polymers are produced.

The organomonolithium compound and allyl-substituted tertiary amine can be reacted together in the presence of an inert hydrocarbon diluent which usually results in the formation of a precipitated initiator. The inert hydrocarbon diluents including paraflins, cycloparafiins, or aromatics generally containing from 4 to 10 carbon atoms per molecule are suitably employed. Examples of suitable hydrocarbons which can be used are isobutane, n-pentane, cyclohexane, benzene, toluene, and the like.

Following the reaction between the allyl-substituted tertiary amine and the organormonolithium compound the precipitated initiator thus formed can be solubilized by the addition of a solubilizing monomer such as a conjugated diene containing from 4 to 6 carbon atoms per molecule; exemplary are butadiene, isoprene, piperylene, 2,3-dimethyl-1,3-butadiene, and the like, or a monovinyl-substituted aromatic compound such as styrene and the like. Generally from about 2 to 15 moles of solubilizing monomer per mole of organomonolithium compound is sufficient to solubilize the precipitated initiator. Larger and smaller amounts can be employed.

The organomonolithium compounds that are employed according to this invention can be represented by the formula R"Li; wherein R" is an aliphatic, cycloaliphatic, or aromatic hydrocarbon radical, or combinations thereof, preferably containing from 2 to 20 carbon atoms per molecule. Exemplary of some of these organomonolithium compounds are ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-octyllithium, p-decyllithium, n-eicosyllithium, phenyllithium, 2- naphthyllithium, 4-butylphenyllithium, 4-tolyllithium, 4- phenylbutyllithium, cyclohexyllithium, 3,5-di-n-heptylcyclopentylbutyllithium, and the like. The alkyllithium compounds are preferred for employment according to this invention, especially those wherein the alkyl group contains from 3 to 10 carbon atoms.

Allyl-substituted tertiary amines employed according to this invention can be represented by one of the following general formulas:

( R N or where n is an integer from 1 to 6; m is O or an integer from 1 to 6; R is hydrogen or an alkyl group containing from 1 to 3 carbon atoms; and R is an alkyl, cycloalkyl, or aryl hydocarbon radical, or combination thereof such as cycloalkylaryl, containing from 1 to 12 carbons, or an allyl radical of the formula:

Exemplary of some of these allyl-substituted tertiary amines are triallylamine;

butyldiallylamine; tetraallylmethylenediamine; 4,7,10-triallyl-4,7,IO-triaza-1,12-tridecadiene;

n-dodecyldiallylamine;

phenyldiallylamine;

(4-cycohexylphenyl) diallylamine;

cyclopentyldiallylamine;

( 3-phenylcyclohexy1) diallylamine;

tri- 2,3-dimethy-2- (3-butenyl) amine;

methyldi- (2-n-propylallyl) -amine;

tetraallylhexamethyleuediamine;

3 ,6-diallyl-3,G-diazaoctane;

bis-(l,48-diallylamino)-7,14,21,28,3 5,42-hexamethyl- 7,14,21,28,35,42-hexaazaoctatetracontane;

4-phenyl-6-ethyl 9 cyclohexyl l3 methyl- 1 8-cyclododecyl-24- (4-ethylphenyl) 3 l 3-methylcyclopenty 4,6,9, 13, 18,24,3 l-heptaaza- 1,3 3-tetratriacontadiene;

4,7, -triallyl-2,3 ,3 ,11,1l, l2-hexamethyl-4,7,l0-triaza- 1,12-tiadecadiene;

4,7-diphenyl-4,7-diazal ,9-decadiene;

and the like.

The relative amounts of organomonolithium compounds and allyl-substituted tertiary amine can be expressed in terms of gram moles of organomonolithium compound per gram mole of allyl-substituted tertiary amine or in terms of gram moles of organomonolithium compound per allyl group in one mole of the allyl-substituted tertiary amine. The quantity of organomonolithium compound employed according to this invention for the preparation of these multifunctional initiators is in the range of from about 0.2 to 2, preferably fom 0.5 to 1.5 moles of organomonolithium compound per each allyl group in each mole of allyl-substituted tertiary amine.

The temperatures employed for preparing the initiators of this invention can vary considerably but are generally in the raneg of about 25 to 100 C., preferably 50 C. or above. The organomonolithium compound and theallylsubstituted tertiary amine are recated together generally in the range of about 1 minute to 16 hours, preferably from 10 minutes to 4 hours.

While my invention is not dependent upon any particular reaction mechanism, it is believed that both addition and metallation reactions are involved during initiator preparation. 'This invention makes it possible for higher functionality to be obtained than can ordinarily be achieved when preparing the multifunctional initiators.

The polymers which can be prepared by employing the initiators of this invention are homopolymers made from conjugated dienes containing from about 4 to 12, preferably 4 to 8, carbon atoms per molecule; copolymers of two or more conjugated dienes; homopolymers made from monovinyl-substituted aromatic compounds containing 8 to 20, preferably 8 to 12, carbon atoms per molecule;

copolymers of two or more monovinyl-substituted aromatic compounds; and copolymers of conjugated dienes and monovinyl-substituted aromatic compounds. Homopolymers can range from low molecular weight liquids to solid polymers. Copolymers can be random or block copolymers and this invention provides a method for obtaining rubbery block copolymers of conjugated dienes and monovinyl-substituted aromatic compounds that possess high green tensile strength. Multiple blocks of polymerized monovinyl-substituted aromatic compounds are essential to obtaining high green tensile strength. Resinous block copolymers can be prepared by polymerizing a predominant amount of monovinyl-substituted aromatic compound and a minor amount of conjugated diene.

High impact resins with a high degree of clarity and other good properties can also be prepared using the multifunctional initiators of this invention the polymerization temperature can vary over a broad range and is generally in the range of about 70 to 150 C., and it is preferred to operate at a temperature above C. It is also preferred that the polymerization be conducted in the presence of a suitable inert hydrocarbon diluent such as the parafiins, cycloparafiins, and aromatics containing about 4 to 10 carbon atoms per molecule. Exemplary of suitable diluents are benzene, toluene, xylene, cyclohexane, methylcyclohexane, n-butane, n-hexane, n-heptane, isooctane, mixturs of these, and the like.

As hereinbefore stated when a polymerization is conducted in the presence of a multifunctional initiator of this invention, the unquenched polymerization mixture has a branched structure and the branches contain terminal lithium atoms. Treatment with various agents such as carbon dioxide, epoxy compounds, and the like, yield polymers in which the functional groups of these treating agents have replaced the terminal lithium atoms on the several polymer branches. These treated polymers can be cured easily to form a tight network by reaction with various polyfunctional reagents. As an example, low molecular weight liquid polybutadiene containing multple terminal carboxyl groups can be cured to a solid polymer with a polyfunctional azirdinyl compound or a polyfunctional epoxy compound.

The initiators of this invention are also useful for the polymerization of butadiene when present in a stream which contains appreciable amounts of compounds such as 1,2-butadiene, propadiene, acetylenes, and aldehydes.

The amount of initiator to be used in the polymerization process depends upon the particular multifunctional polymerization initiator employed and the type of polymer desired. An effective initiator level is normally in the range of about 0.25 to 100, preferably 1 to 50 milliequivalents of lithium per grams of monomer (m.e.h.m.) charged to the polymerization system.

The milliequivalents of lithium can be conveniently determined by an alkalinity titration of a known volume of the reaction mixture containing the multifunctional initiator. Said alkalinity titration employs standardized acid, e.g., HCl and an indictaor such as phenolphthalein to determine the end-point of titration. The alkaline normality thus obtained provides a value for the milliequivalents of lithium per milliliter of reaction mixture containing the multifunctional initiator. The alkalinity concentration (normality) first determined is then employed for charging a known quantity of milliequivalents of lithium in polymerization recipes employing the multifunctional initiators of this invention.

Illustrative of the foregoing discussion and not to be interpreted as a limitation on the materials herein employed, or on the scope of my invention, the following examples are provided.

EXAMPLE I Multifunctional polymerization initiators were prepared from sec-butyllithium and tetraallylmethylenediamine by adding a l M solution of tetraallylmethylenediamine in cyclohexane and a 1.2 M solution of sec-butyllithium in cyclohexane to 15 milliliters of cyclohexane previously charged to reactor. The amounts of reactants employed were such as to give 4:1 and 5:1 mole ratio of sec-butyllithium to the amine compound. The temperature was adjusted to 70 C. for two hours while the mixtures were agitated. Each of the initiators were employed for the polymerization of butadiene according to the following recipe:

1,3-butadiene, parts by weight 100 Cyclohexane, parts by weight 790 Initiator, m.e.h.m. Variable Temperature, C. 50 Time, hours 20 1 M.e.l1.m.:gi-am milliequivalents lithium per 100 grains of 111011011181.

cyclohexane was charged to the reactor followed by a nitrogen purge, the butadiene, and the initiator respectively. At the conclusion of each polymerization a 10 weight percent solution of the antioxidant, 2,2-methylene-bis(4-methyl-6-tert-butylphenol), in a mixture of equal parts by volume of toluene and isopropyl alcohol, was added in an amount sufficient to provide one part by weight of the antioxidant per 100 parts by weight of the polymer. The polymer was coagulated in isopropyl alco- 1101 then separated and dried. The' results of the polymerization are presented in Table I.

TABLE I Initiator Cold 1 Mrcrostructure Mole ratio, Conv., fiow, Inll. Gol, ML-4 at 3 Percent 4 Run No BuLizamino Meq. percent lug/min. vise. percent 212 F. Cis Trans vinyl 1 As described in U.S. Pat. 3,218,306, column 6, lines 61-66.

2 Determined as described in [1.8. Pat. 3,215,679, notes (B) and (0), column 11.

3 ASTM-D-1646-63 4 Determined as described in U.S. Pat. 3,215,679 note (K), column 12.

5 Initiator stored at room temperature (about 25 6 Not determined.

The above data demonstrate that high molecular weight, gel-free polymers with little, if any, coldfiow were obtained by employing the initiators of this inven- C.) for 48 hours prior to use without agitation.

agitated. These initiators were employed for the polymerization of butadiene using the following recipe:

tion. The data from Runs 1 and 2 also show that these fs i ggig gig ag fi 2 initiators have a desirable degree of stability on storage. Initiator meilm g These results further indicate that branched polymers Temperature were obtained from polymerizations initiated in the prcs- Time hours 50 once of my multifunctional initiators. At the initiator levels employed in the above example use of the butyllithium initiators of the prior art would have resulted in liquid polymers.

EXAMPLE II An initiator was prepared employing three millimoles of sec-butyllithium per one millimole of triallylamine by reaction thereof at 70 C. for 3 hours in sufficient cyclohexane to produce a 1 N solution in alkyllithium. The multifunctional initiator thus prepared and n-butyllithium, employed as a control, were separately employed for the polymerization of 1,3-butadiene according to the TABLE III I t H v followmg polymerization reclpe. i Mimostructure, percent 1,3-Butadiene, parts by weight 100 40 Run BuLlIamine Percent Cis Trans Vinyl Cyclohexane, parts by weight 790 i 1 3 Mg 42,3 492 5 Initiator Variable 2 411 Not determined Temperature, C. Variable Time, hours Vaviable Tiles? data SllOW t l quld low-vinyl Containing poly- Conversion, percent 100 mers Wlth termlnal Y Y groups can be obtained when The cyclohexane was charged to the reactor, followed by nitrogen purge, the addition of the butadiene and initiator, respectively. The reaction conditions and results are reported in Table II.

using the initiators of this invention.

EXAMPLE IV Initiators were prepared from tetraallylmethylenediamine and triallylamine by reacting sec-butyllithium with TABLE II each amine. The initiator from tetraallylmethylenediamine T Initiator 0 Mn MIA at wasl pretparegbas iilesltlzribed in Example III using a 6:1 mm, 0 9w mo e ra 1o 0 ut 1t ium to amine com ound. h er hours Mehm't Mhm'g 212 initiator was prep ared by reacting a 1.0 r iiolar sb luii r i of 8.8 g; triallylamine in cyclohexane with a 1.49 molar solution I 66 of sec-butyllithium in cyclohexane in amounts such that 1. 75 8.0 8.8 the mole ratio of butyllithium to triallylamine was 3:1.

- 1 100 The reactants were agitated for 3 hours at 70 C.

82 22 These initiators were employed for the preparation of 41:10 22 51 multiblock copolymers of butadiene and styrene. The

4 1.15 48 29 recipes were as follows:

I Mehm=gram milliequivalents lithium per 100 grams of monomer. 2 Mhm=millimo1es n-butyllithium per 100 grams of monomer.

3 Multifunctional initiator. A B 4 n-B ntyllithium initiator, control. 1,3 butadiene. parts by weight 5o 60 The above results etfectively demonstrate that the iv giiifgxfii ef iltl fi$5.555: 38 38 multifunctional initiators of this invention produce polyg tg 8 meme butadiene possessing reduced coldflow tendencies when iii compared to polybutadiene produced when employing cmvel'sionipemen the n-butyllithium initiator.

EXAMPLE III Initiators were prepared by reacting variable quantities of a 1.25 molar solution of sec-butyllithium in cyclohexane with a 1.0 molar solution of tetraallylmethylenediamine for one hour at C. while the mixtures were Cyclohexane was charged to the reactor first followed by a nitrogen purge. The styrene, butadiene, and initiator were added in that order respectively. Green tensile strength, elongation, and polystyrene content were determined for each of the polymers produced and the data are presented in Table IV.

TABLE IV Initiator Run Tensile, Elong,, Polystyrene! No, Recipe From M.e.h.m. p,s,i, percent percent 1 A Tetraallylmcthylene- 8 1,600 530 38.3

diamine, 2 B Triallylamine 4 1,100 1,100 27.7 3 B .....de 6 1,450 2,070 28.5 4 B 8 2,000 l, 700 28.4

l Determined by ASTM-D-412-62T Sci,, 1, 420 (1916),

The results of the polystyrene determinations demonstrate that multiblock copolymers were produced. The products had high green tensile strength which is also in dicative of the type of block copolymcr obtained. 1,3- butadiene/styrene block copolymers in which one end of the polymer is a polybutadiene segment and the other end is a polystyrene segment have green tensile strengths that are too low to measure on the Instron Tensile machine.

EXAMPLE V An initiator was prepared by reacting sec-butyllithium with triallylamine according to the following recipe:

sec-Butyllithium, mmoles 60 Triallylamine, mmoles Cyclohexane, sufiicient to give a 1.0 molar concentration with respect to sec-butyllithiurn.

Temperature, C. 70

Time, minutes 45 The above-prepared initiator designated initiator A, was employed for the random copolymerization of butadiene with styrene. A control run employing n-butyllithiurn designated initiator B, was similarly employed. The following polymerization recipe was used:

POLYMERIZATION RECIPE 0 1,3-butadiene, parts by weight 75 75 Styrene, parts by weight 25 Tetrahydroiuran, parts by weight. 1, 5 1. 5 Cyclohcxane, parts by \veithg 1, 000 790 Cyclohcxane, parts by weithg 1, 000 079 Initiator A, mchm 5 Initiator B, rnlim 1.15 Temperature C 50 70 Time, minutes 180 90 Conversions, percent 100 100 Cyclohexane was charged to the reactor followed by a nitrogen purge. Butadiene was added followed by the styrene, tetrahydrofuran and initiator respectively. The results of the polymerization are presented in Table V. Run 1 represents the n-butyllithium initiator and Run 2 the initiators of this invention.

TABLE V.RAW RUBBER PROPERTIES Run 1 Run 2 ML-4 at 212 F Mici'costructure, percent:

Trans.

Vinyl Styrene, percent Polystyrene, percent. Inherent viscosity. Ge., percent..." Cold flow, mg./m

I Not determined.

I I l I I renown-i 3" PM? ooooooroooo COMPOUNDING RECIPE Parts by weight Rubber High abrasion furnace black 50 Zinc oxide 3 Stearic acid 3 Stearic acid 2 Flexamine 1 2 1 Aromatic oil (Philrich 5 10 Sulfur 1.75 N-cyclohexyl-Z-benzothiazolesulfenamide 1.2

TABLE VI [Physical properties, cured 30 minutes at 307 E] Run 1 Run 2 300% modulus, p.s.i 1, 530 1, 455 Tensile, p.s.i 2, 970 3, 380 Elongation, percent 490 54 Elongation, perccnt 490 540 Max. tensile at 200 F., 1, 196 Tear strength at 200 0., lb./ MT, F 53 59.6 Resilience, pereent 66 66.0 Shore A hardness 57. 5

I Not determined.

The data show that random copolymers with good vulcanizate properties were obtained using the initiators of this invention.

EXAMPLE VI The preparation of the multilithium initiators of this invention and gas-liquid chromatography analysis of the reaction of sec-butyllithium with triallylamines is demonstrated in this example.

The reaction of triallylamine (3 gram millimoles) with sec-butyllithium (9 gram millimoles) was examined by gas-liquid chromatography (GLC) analysis. In this run isobutane (1 gram millimole) was added to the reaction mixture as an internal standard and gas phase samples (500 microliters) were withdrawn at various times and analyzed by GLC to follow the disappearance of the sec-butyllithium. GLC analyses were performed with a Perkin-Elmer Model 154 Vapor Fractometer. Analyses were made at 25 C. with helium (25 p.s.i.g.) as the carrier gas. The chromatography column was 16 feet, A1 inch OD copper tubing packed with a support of crushed fire'brick (Chromasorb P obtained from Johns- Manville Co.) containing 17 weight percent hexamethylphosphoramide. The results of these analyses are shown in the table below.

n-Butane, gram millimoles found: sec-BuLi After mixing 0.53

Analysis made immediately after reactants were mixed. The amount found represents the destruction of see-biityllithium by rapid reacting impurities or other fast reactions.

Analysis made after 1 hour at 70 C. The amount found represents destruction of sec-butyllithium by slow reacting impurities or metallation of triallylamine or other slow reaction.

0 Analysis made after reaction mixture was hydrolyzed with sufficient water to completely react with all the sec-butyllithium initially charged. The amount found indicates only 0.02 millimole of sec-busyllithiiim was unreacted at this time.

This amount consumed by reaction with triallylamine was determined by the difference between the amount of sec-bntyllithium charged (9 millimoles and the amount of n-butnnc found after hydrolysis (2.05 millimoles).

The above results demonstrate that at least 6.95 millimoles of sec-butyllithium were consumed by reaction with 3 millimoles of triallylamine. These results further indicate that for each mole of reacted triallylamine there is attached thereto an average of at least 2.31 lithiums which further demonstrates the multifunctional nature of the initiators of this invention.

As will be evident to those skilled in the art, various modifications of this invention can be made or followed, in light of the disclosure and discussion herein set forth, without departing from the scope and spirit thereof.

I claim: 1. A multifunctional polymerization initiator which forms by steps comprising admixing components consisting essentially of an allyl-substituted tertiary amine and an organomonolithium compound wherein about 0.2 to 2 moles of said organomonolithium compound is provided per each allyl group in each mole of said allyl-substituted tertiary amine,

wherein said admixing is conducted at a temperature of from about 25 C. to 100 C.,

wherein said organomonolithium compound is R"Li wherein R" is a hydrocarbyl radical containing from 2 to 20 carbon atoms and is aliphatic, cycloaliphatic, aromatic or a combination thereof,

said allyl-substituted tertiary amine is or (II) R N[ (-CHR' ,,-NR] (CHR' -NR wherein n is an integer from 1 to 6, m is or an integer from 1 to 6, R is hydrogen or an alkyl group containing from 1 to 3 carbon atoms, and R is a hydrocarbon radical containing from 1 to 12 carbon atoms and is alkyl, cycloalkyl, aryl, a combination thereof, or an allyl radical HQ(./ECRICR'2 such that said allyl-substituted tertiary amine as represented by said 1 and 2 contains at least two allyl radicals per molecule.

2. The multifunctional polymerization initiator of claim 1 wherein about 0.5 to 1.5 moles of said organomonolithium compound is provided per each allyl group in each mole of said allyl-substituted tertiary amine.

3. The multifunctional polymerization initiator of claim 2 wherein said admixing of components is conducted in the presence of an inert hydrocarbon diluent and said components are allowed to react in the range of about one minute to sixteen hours.

4. The multifunctional polymerization initiator of claim 3 wherein said admixing of components is conducted at a temperature of C. or above, wherein said components are allowed to react in the range of about 10 minutes to 4 hours, and wherein said organomonolithium compound is sec-butyllithium and said allylsubstituted tertiary amine is tetraallylmethylenediamine or triallylamine.

5. The multifunctional polymerization initiator of claim 2 further including the step of adding a solubilizing monomer to the reaction product of said organomonolithium compound and said allyl-substituted tertiary amine, wherein said solubilizing monomer is a monovinylsubstituted aromatic compound, a conjugated diene, or mixture thereof, and about 2 to 15 moles of said solubilizing monomer are provided per mole of said organomonolithium compound.

References Cited UNITED STATES PATENTS 3,206,519 9/1965 Eberhardt 252431/N X 3,450,795 6/ 1969 Langer 252--431/N X 3,451,988 6/1969 Langer 252-431/N X 3,536,679 10/1970 Langer 252-432/N X PATRICK P. GARVIN, Primary Examiner US. Cl. X.R. 

